Image processing system, in-vehicle camera system with image processing system, and vehicle with camera system

ABSTRACT

An image processing device is enabled to appropriately restore a contrast of a camera image. An in-vehicle camera has an image capture unit that captures images of surroundings of a vehicle through a windshield of the vehicle. A hood is disposed below the image capture unit and is present within an angle of view of the image capture unit. The control unit includes a luminance acquirer that acquires a luminance parameter indicating a degree of luminance of the hood appearing in a camera image, a whitish blur degree calculator that calculates a degree of whitish blur of the camera image caused by a reflection of natural light by the hood and the windshield in accordance with the luminance parameter, and a contrast corrector that corrects a contrast of the camera image in accordance with the whitish blur degree.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is based on and claims priority to JapanesePatent Application No. 2020-213918, filed on Dec. 23, 2020 in the JapanPatent office, the entire disclosure of which is hereby incorporated byreference herein.

BACKGROUND Technical Field

The present disclosure relates to an image processing system, anin-vehicle camera system with the image processing system, and a vehiclewith the in-vehicle camera system.

Related Art

In a known camera system employed in vehicles, a camera is disposedclose to an inside of a windshield in the vehicle. In such a system,since a dashboard is reflected by an inner surface of the windshield andthe reflection mixes with a camera image when forward surroundings arecaptured by the camera, a hood is generally attached to the camera toprevent the image of the dashboard from being mixed with the cameraimage. Hence, in a known hooded camera, the hood being present in thecamera image is detected (i.e., determined) based on the camera image,and only an image area where the hood is absent is extracted from thecamera image to be used when the hood is present in the camera image.Hence, according to the known hooded camera, an amount of video datatransmitted externally is reduced even if the quality of the appearanceof the video is maintained.

Further, when a hooded camera is disposed close to the inside of thewindshield of the vehicle, natural light is reflected by both the hoodand the inner side of the windshield in this order. As a result, acamera image as a whole is highly likely to be blurred in white therebygenerating a whitish image resulting in deterioration of a contrast ofthe camera image. Hence, a technology of avoiding degradation of thecontrast caused by such whitish blur is called for in the in-vehiclecamera with the hood.

Accordingly, the present disclosure has been made to address and resolvethe above-described problems, and it is an object of the presentdisclosure to provide an image processing system capable ofappropriately restoring a contrast of a camera image.

SUMMARY

Accordingly, one aspect of the present disclosure provides a novel imageprocessing system used with an in-vehicle camera system that includes:an image capture unit to capture images of surroundings of a vehicle ascamera images through a windshield of the vehicle; and a hood to preventan interior of the vehicle from being reflected in the windshield andbeing captured by the image capture unit together with the surroundingsof the vehicle. The hood is disposed below the image capture unit and ispresent within an angle of vision of the image capture unit. The imageprocessing system includes: a luminance parameter acquirer to acquire aluminance parameter indicating a degree of luminance of an image of ahood reflected in the camera image; and a whitish blur degree calculatorto calculate a degree of whitish blur of the camera image as a whitishblur degree in accordance with the luminance parameter. The whitish bluris caused when natural light is reflected by both the hood and thewindshield. The image processing system further includes a contrastcorrector to correct a contrast of the camera image in accordance withthe whitish blur degree.

Another aspect of the present disclosure provides a novel in-vehiclecamera system that comprises: an image capture unit to capture images ofsurroundings of a vehicle as camera images through a windshield of thevehicle; and a hood to prevent an interior of the vehicle from beingreflected in the windshield and being captured by the image capture unittogether with the surroundings of the vehicle. The hood is disposedbelow the image capture unit and is present within an angle of vision ofthe image capture unit. The camera system also includes theabove-described image processing system.

Yet another aspect of the present disclosure provides a novel vehiclehaving an automatic driving function and a drive recorder. The vehicleincludes a camera system disposed in a cabin close to a windshield, andthe above-described camera system.

Hence, according to one embodiment of the present disclosure, the hoodis attached to the camera and is present within an angle of view of theimage capture unit. Then, the luminance parameter indicating a degree ofluminance of the hood reflected to the camera image is acquired.Further, in accordance with the luminance parameter of the hood, adegree of whitish blur (i.e., whitish blur degree) of a camera imagecaused by natural light reflected by both the hood and the windshield iscalculated. Then, a contrast of the camera image is corrected inaccordance with the degree of the whitish blur. Here, the degree ofwhitish blur is proportional to an intensity of reflection of naturallight in the hood. Also, the luminance parameter of the hood in thecamera image (i.e., an image of the hood) is proportional to theintensity of the reflection of the hood. Hence, the contrast of thecamera image can be appropriately restored by correcting the contrast bythe degree of whitish blur calculated in accordance with the luminanceparameter of the hood.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present disclosure and many of theattendant advantages of the present disclosure will be more readilyobtained as substantially the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings, wherein:

FIG. 1 is a diagram schematically illustrating a configuration of acamera system mounted on a vehicle according to one embodiment of thepresent disclosure;

FIG. 2 is a block chart principally illustrating a configuration of acamera system according to one embodiment of the present disclosure;

FIG. 3 is a side view illustrating the camera system from one sidethereof according to one embodiment of the present disclosure;

FIG. 4 is also a side view illustrating the camera system from one sidethereof according to one embodiment of the present disclosure;

FIG. 5 is a diagram schematically illustrating a camera image capturedby an image capture unit according to one embodiment of the presentdisclosure;

FIG. 6 illustrates a graph illustrating a relation between a hood pixelvalue (i.e., a pixel value of a hood image) and a value of luminanceaccording to one embodiment of the present disclosure;

FIG. 7 is a flowchart illustrating a sequence of correcting a contrastof a camera image according to one embodiment of the present disclosure;

FIG. 8 is diagram illustrating a relation between a vertical position inthe camera image and a correction value according to a firstmodification of the present disclosure;

FIG. 9 is a flowchart illustrating a sequence of correcting a contrastof an image according to a second modification of the presentdisclosure;

FIG. 10 is a diagram illustrating a running state of a vehicle accordingto the second modification of the present disclosure;

FIG. 11 is a flowchart illustrating a sequence of calculating a timemean value of a hood pixel value according to a third modification ofthe present disclosure;

FIG. 12 is a flowchart illustrating a sequence of correcting a contrastof an image according to a fourth modification of the presentdisclosure; and

FIG. 13 is a graph illustrating a compression-extension function (f)calculated when a hood pixel value is converted into a value ofluminance.

DETAILED DESCRIPTION

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views thereof,and to FIG. 1 , an outline of a camera system will be initiallydescribed. The camera system of this embodiment is mounted on a vehicleand captures images of surroundings in front of the vehicle by using anin-vehicle camera.

FIG. 1 illustrates a configuration of the camera system mounted on thevehicle 50. As shown, a camera 10 is disposed close to an inner side ofa windshield 51 in the vehicle 50. The camera 10 has an image captureunit 20 that captures images of surroundings (e.g., a scenery) of thevehicle 50. The camera 10 serves as a front camera and is positioned tocapture a given region in front of the vehicle 50 over the wind shield51. Thus, the given region of the surroundings serves as an imagecapturing region. Accordingly, when a dashboard 52 or the likepositioned in a vehicle interior is reflected by the windshield 51, animage of the dashboard 52 is highly likely to be included in a cameraimage captured by the image capture unit 20. Hence, a hood 11 isgenerally disposed on a front lower side of the image capture unit 20 toprevent the image of the dashboard 52 or the like from appearing in theimage. The hood 11 may be integral with or separately from a housing ofthe camera 10.

FIG. 2 illustrates a configuration of the camera 10. The camera 10includes an image capture unit 20 and a control unit 30. The imagecapture unit 20 includes an optical system 21 and image sensor unit 22.

The optical system 21 includes a lens, an aperture or a diaphragm and ashutter or the like (not shown). The lens focuses visible light incidentthereto on the image sensor unit 22. The diaphragm adjusts a quantity ofvisible light having passed through the lens in accordance with adiaphragm value. The visible light having passed through the diaphragmenters the image sensor unit 22. The shutter opens and closes at a givenshutter speed during image capturing. With this, an exposure process isperformed in accordance with the shutter speed during an exposureperiod.

The image sensor unit 22 may include a CMOS (Complementary Metal OxideSemiconductor) sensor or multiple CCD (Charge Coupled Device) sensorsand the like. The image sensor unit 22 outputs an electrical signalindicating intensity of the visible light incident thereto. Theelectrical signal is then amplified with a given gain and is output tothe control unit 30.

The control unit 30 is a microcomputer including a CPU (CentralProcessing Unit), a ROM (Read Only Memory), and a RAM (Random AccessMemory) or the like. The control unit 30 generates image data inaccordance with the electrical signal output from the image sensor unit22. The control unit 30 designates (i.e., determines) image capturingconditions for operating the image capture unit 20. The image capturingcondition may include a shutter speed, a diaphragm value, and a gain foramplifying the electrical signal output from the image sensor unit 22 orthe like. The image capture unit 20 captures images in accordance withthe image capturing conditions designated by the control unit 30. Hence,the control unit 30 acts as an image processing system in the presentdisclosure.

Further, the vehicle 50 includes a driver assistance system 40 thatperforms driver assistance control for controlling the vehicle. Thedriver assistance system 40 receives image data from the control unit 30and performs various driver assistance control activities based on theimage data. Specifically, the driver assistance system 40 recognizesdemarcation lines, such as white lines, etc., other vehicles, andpedestrians based on images of the surroundings in front of the vehicle.The driver assistance system 40 also recognizes bicycles and otherobjects, such as structures, etc., based on the image data. Then, basedon these recognition results, the driver assistance system 40appropriately performs the driver assistance controls including lanekeeping control to suppress lane deviation by an own vehicle, pre-crashsafety control to avoid collision with objects, and tracking control oftracking other vehicles preceding the own vehicle to control the ownvehicle to follow the other vehicles or the like.

With the above-described configuration shown in FIG. 1 , natural lightis reflected first by the hood 11 and then by the inner side of thewindshield 51 as the hood 11 is disposed below the image capture unit 20close to the inside of the windshield 51 in the vehicle 50. Hence, aphenomenon, in which a camera image captured by the image capture unit20 is blurred in white occurs when viewed as a whole. Specifically, awhitish image is generated. That is, as shown in FIG. 3 , when a lightsource 60 such as the sun, etc., is located ahead of the vehicle 50,light from the light source 60 passes through the windshield 51 and isreflected by a surface of the hood 11. Then, the light reflected by thesurface of the hood 11 reaches and is reflected by the inner side of thewindshield 51. Then, the light reflected by the inner side of thewindshield 51 enters the image capture unit 20, thereby blurring thecamera image in white (hereinbelow simply referred to as whitish blur).As a result, the whitish blur is likely to decrease a contrast of thecamera image.

In view of this, according to this embodiment, the control unit 30corrects the contrast of the camera image in accordance with a degree ofwhitish blur (cd/m{circumflex over ( )}2) of the camera image. Hence, asshown in FIG. 4 , a part of the hood 11 is positioned ahead of the imagecapture unit 20 within an angle of view a of the image capture unit 20as a prerequisite structural condition. Accordingly, the hood 11 appearsin the camera image captured by the image capture unit 20.

FIG. 5 illustrates a camera image captured by the image capture unit 20.Specifically, in this camera image, a partition line drawn on a road andother vehicles running ahead of the vehicle 50 on the road are captured.At the same time, the hood 11 also appears in a lower part of the cameraimage.

As described earlier, due to reflection of natural light in both thehood 11 and the inside of the windshield 51, the camera image includingthe hood 11 shown in FIG. 5 blurs in white (i.e., blurry) when viewed asa whole. In such a situation, however, a degree of the whitish blur ofthe camera image is proportional to that of intensity of the naturallight reflected by the hood 11. Further, the degree of the intensity ofthe natural light reflected by the hood 11 can be known based on a valueof a pixel (e.g., an average of pixel values, herein below the sameunless otherwise specified) corresponding to the hood 11 in the cameraimage.

Further, since a degree of whitish blur of the camera image issubstantially equivalent to an amount of light (i.e., flare) reflectedby an interior side of a windshield of a vehicle, the degree of thewhitish blur of the camera image can be represented by a value ofluminance [cd/m{circumflex over ( )}2], wherein cd represents Candela.

In view of this, the control unit 30 calculates the whitish blur degreein accordance with the hood pixel value generated in the camera imageand corrects a contrast of the camera image in accordance with thewhitish blur degree. Specifically, a luminance acquirer 31 is providedin the control unit 30 and acquires a luminance parameter indicating adegree of luminance of the hood 11 appearing in the camera image.Specifically, the control unit 30 (i.e., the luminance acquirer 31)calculates hood pixel values generated in the camera image and convertsthe hood pixel values into a value of luminance.

Such a conversion from the hood pixel values into the value of luminanceis performed as described below.

First, a pixel value (e.g., an average of pixel values) corresponding tothe hood is linearly converted by using the below described equalityshown in FIG. 13 , wherein Y represents a linearly extended pixel value(linear pixel value), f represents a compression-extension functionwhich varies in accordance with a setting value, such as a shutterspeed, a gain, etc., designated when an image is captured, and Xrepresents a compressed pixel value.Y=f(X)

For example, as shown in the drawing, if X (e.g., 2500 value) is locatedbetween points as plotted, Y (e.g., 9280 value) is found byinterpolating these points.

Then, the linear pixel value of the hood is converted into a luminanceof the hood by using the below described formula, wherein A represents acoefficient varying in accordance with the setting value, such as theshutter speed, the gain, etc., designated when the image is captured.Luminance of hood=A*Y

Hence, in this embodiment, the value of luminance of the hood imageportion in the camera image acts as the luminance parameter.

More specifically, as shown in FIG. 5 , a given region M1 is specifiedin the camera image corresponding to the hood 11, and the hood pixelvalue generated in the given region M1 is calculated. In such asituation, the hood pixel value may be calculated by averaging pixelvalues obtained at multiple points within the given area M1. Otherwise,the hood pixel value can be calculated by averaging hood pixel valuesgenerated during a given time period per time.

Then, the luminance acquirer 31 converts the hood pixel value to a valueof luminance based on a relation therebetween as shown in FIG. 6 . Thatis, it is desirable to convert the hood pixel value into the luminancevalue in accordance with an image capturing condition for controllingthe image capture unit 20, such as a shutter speed, a gain, etc. This isbecause the relation between the hood pixel value and the luminancevalue changes as the image capturing condition changes. In view of this,multiple relations between the hood pixel value and the luminance valueare indicated in FIG. 6 , and it is understood therefrom that when theshutter speed is faster, the hood pixel value is converted into agreater luminance value than when the shutter speed is slower even ifthe hood pixel value is substantially the same. Here, the imagecapturing condition is designated corresponding to a driver assistancefunction used in the vehicle 50. Hence, the shutter speed may be faster(i.e., increased) when tracking control of tracking another vehicle isperformed in addition to the lane keep control and the pre-crash safetycontrol performed normally than when the tracking control of the othervehicle is not performed but the lane keeping control and the pre-crashsafety control are performed. The shutter speed is also desirablyincreased until right before a time when the vehicle and a road sign tobe recognized pass each other to suppress blurring of an image thereof.However, the shutter speed may be slower (i.e., decreased less) than alight emission cycle of an electronic information board that generatespulse emission, when the electric information board is to be recognized.

Further, a whitish blur degree calculator 32 is provided in the controlunit 30 and calculates a degree of whitish blur in the camera image inaccordance with the luminance value (i.e., parameter) calculated by theluminance acquirer 31. For example, the degree of whitish blur may becalculated by multiplying the luminance value by a given coefficient. Insuch a situation, since a degree of reflection of natural light in aninner side of the windshield changes in accordance with an angle ofinclination of the windshield 51, the given coefficient may bedetermined in accordance with the angle of inclination of the windshield51.

Specifically, a degree of whitish blur W (cd/m{circumflex over ( )}2) isrepresented by the below described equality, wherein B represents of areflectance coefficient of a windshield of a vehicle varying inaccordance with an angle of the windshield, etc.W=Luminance of hood*B

Further, a contrast corrector 33 is provided in the control unit 30 andcorrects a contrast of the camera image in accordance with the degree ofwhitish blur. Specifically, the whitish blur degree is used incorrecting the contrast of the camera image as a correction value, andis evenly subtracted from a value of each of the pixels in the entireimage.

Next, an exemplary sequence of correcting a contrast of a camera imagewill be described herein below with reference to FIG. 7 . The controlunit 30 repeatedly executes this correction process in a given cycle.

That is, in step S11, the acquirer 31 acquires a hood pixel value from acamera image captured by the image capture unit 20. In step S12, theacquirer 31 acquires an image capturing condition, such as a shutterspeed, a gain, etc., used by the image capture unit 20. In the followingstep of step S13, the hood pixel value is converted into a luminancevalue in accordance with the image capturing condition acquired in stepS12.

Subsequently, in step S14, a whitish blur degree is calculated bymultiplying the luminance value calculated in step S13 by a givencoefficient. In step S15, the contrast of the camera image is correctedin accordance with the whitish blur degree serving as the correctionamount.

Further, in step S16, various image processing, such as noise reductionof reducing a noise of the camera image caused by the shutter speed orthe gain and the like, edge emphasis of enhancing light and dark bordersof the camera image, etc., are performed. Subsequently, in step S17,image data having been subjected to the contrast correction is output tothe driver assistance system 40.

Hence, as described heretofore, according to this embodiment, variousadvantages can be obtained as will be described herein below.

First, the hood 11 is positioned within the angle of view a of the imagecapture unit 20. Then, the luminance parameter indicating the degree ofluminance of the hood 11 appearing in the camera image is acquired.Subsequently, in accordance with the luminance parameter of the hood 11,the degree of whitish blur of the camera image caused by natural lightreflected by both the surface of the hood 11 and the windshield 51, andthen entering the camera image, is calculated. Then, the contrast of thecamera image is corrected in accordance with the whitish blur degree. Asdescribed earlier, the degree of whitish blur is proportional to theintensity of the natural light reflected by the hood 11. In addition,the luminance parameter of the hood 11 in the camera image is alsoproportional to the intensity of the natural light reflected by the hood11. Accordingly, the contrast of the camera image can be appropriatelyrestored by correcting the contrast thereof by the whitish blur degreecalculated in accordance with the luminance parameter of the hood 11.

Further, as also described earlier, when the camera image blurs inwhite, a relation between a pixel value of the image of the hood 11 anda luminance value thereof changes in accordance with an image capturingcondition, such as a shutter speed, a gain, etc. In view of this,according to this embodiment, since the pixel value is converted intothe luminance value in consideration of the image capturing condition,the whitish blur degree can be appropriately calculated.

That is, by changing the image capturing condition in accordance withthe driver assistance function, images of a scenery or surrounding ofthe vehicle can be captured in accordance with an appropriate imagecapturing condition per driver assistance function.

Herein below, various modifications of the above-described embodimentwill be described with reference to FIGS. 8 to 12 and applicabledrawings.

A first modification will be initially described in detail withreference to FIG. 8 and applicable drawings. In the above-describedembodiment, the control unit 30 performs the contrast correction bysubtracting substantially the same correction value from the pixel valuein each of the pixels of the entire image. However, the presentdisclosure is not limited thereto and can utilize different correctionvalues instead of such a flat contrast correction value. For example,the control unit 30 may calculate correction values showing a magnitudegradient in a vertical direction of the camera image in proportion tothe whitish blur degree. Then, the control unit 30 may correct acontrast of the camera image based on the gradient correction values.That is because it is considered that the upper side of the camera imagehas less whitish blur. By contrast, the lower side of the camera imageis considered to have greater whitish blur. Hence, as shown in FIG. 8 ,a larger correction value is calculated as a position of the cameraimage approaches a lower end of the camera image. By contrast, a smallercorrection value is calculated as the position of the camera imageapproaches an upper end of the camera image. Then, contrast correctionis performed by subtracting different correction values from pixelvalues of all pixels in accordance with a vertical position (e.g., anupper side, a lower side) in the camera image.

Specifically, since the windshield 51 is generally inclined from avertical direction, an upper part of the windshield 51 in front of theimage capture unit 20 is accordingly close to the image capture unit 20.By contrast, a lower part of the wind shield 51 in front of the imagecapture unit 20 accordingly recedes from the image capture unit 20. Insuch a situation, however, an intensity of a light incident on a pixellocated in the upper side of the camera image is likely to be differentfrom that incident on a pixel located in the lower side of the cameraimage. That is, in general, the larger the angle formed by a light beamfrom an object and a normal line of the windshield 51, the greater thereflection of the light beam. By contrast, the smaller the angle, theless the reflection of the light beam. Hence, an angle formed by a lightbeam emitted from the object and reaching the camera image and thenormal line of the windshield 51 becomes increasingly relatively smalleras a position of the camera image receiving the light beam approachesthe upper side of the camera image. By contrast, an angle formed by alight beam emitted from the object and reaching the camera image and thenormal line of the windshield 51 becomes increasingly relatively largeras a position of the camera image receiving the light beam approachesthe lower side of the camera image. Hence, the intensity of the lightincident on the pixel located in the upper side of the camera image isdifferent from that of the lower side of the camera image. As a result,a difference in degree of whitish blur is likely to occur in the cameraimage in the vertical direction. In view of this, correction valueshaving an inclination of magnitude in the vertical direction of thecamera image are calculated, and a contrast of the camera image iscorrected in accordance with the correction values in this modificationas described above. Hence, according to this modification, since thecorrection values can be calculated in accordance with the difference indegree of the whitish blur in the vertical direction in the cameraimage, the contrast of the camera image can be appropriately corrected.

Next, a second modification will be described herein below in detailwith reference to FIG. 9 and applicable drawings. That is, reflection ofsunlight by both the hood 11 and the wind shield 51 generates a whitishimage in the camera image, for example, when the sunlight arrives at theimage capture unit 20 from a front side of the vehicle 50. In otherwords, reflection of the sunlight by both the hood 11 and the windshield 51 does not generate the whitish image in the camera image whenthe sunlight arrives at the image capture unit 20 from a rear side ofthe vehicle 50.

In view of this, according to this modification, a reference value of aluminance parameter for indicating luminance of a pixel in a cameraimage corresponding to the hood 11 is calculated when the image captureunit 20 captures images based on sunlight arriving at the image captureunit 20 from the rear side of the vehicle 50 (hereinafter, simplyreferred to as a rear sunlight). Then, a degree of whitish blur can becalculated based on a luminance parameter of the pixel in a camera imagecorresponding to the hood 11 periodically calculated during running of avehicle and the reference value of the luminance parameter.

Here, the reference value of the luminance parameter is a value obtainedwhen the image capture unit 20 is not directly exposed to sunlight. Thatis, by using a solar radiation sensor 23 acting as a rear sunlightpresence determiner or the like as illustrated in FIG. 2 , presence orabsence of the sunlight directly entering the image capture unit 20 isdetermined based on an output from the solar radiation sensor or thelike, and the reference value is calculated when the sunlight does notdirectly enter the image capture unit 20.

Such a reference value of the luminance parameter can also be determinedduring a designing stage. For example, a pixel value corresponding tothe food can be previously measured in a phase of product development oncondition that sunlight indirectly hits the image capture unit 20 in anordinary shade and is stored as a parameter.

Here, the rear sunlight means an irradiation condition, in which the sunappears in an opposite direction to a direction in which the imagecapture unit 20 captures images. In other words, the rear sunlight meansan irradiation condition, in which the image capture unit 20 isirradiated with sunlight from behind. By contrast, the front sunlightmeans an irradiation condition, in which the sun appears in a directionin which the image capture unit 20 captures images. In other words, thefront sunlight means an irradiation condition, in which the imagecapture unit 20 is irradiated with sunlight from a front side thereof.

FIG. 9 is a flowchart specifically illustrating a sequence of a processperformed in this modification. As shown, the process is carried out inplace of the above-described process shown in FIG. 7 . In the drawing ofFIG. 9 , the same step number as used in FIG. 7 is assigned to the sameprocess, and the description thereof is not repeated (i.e., omitted)herein below. However, respective processes performed in steps S21 andS22 are newly employed in this modification in addition to all of thesteps of FIG. 7 as shown In FIG. 9 .

Specifically, as shown in FIG. 9 , hood pixel values are obtained andare converted into luminance values in steps S11 to S13. Then, it isdetermined in step S21 if the rear sunlight condition is present. Forexample, based on information, such as a current position of the sun, arunning direction of the vehicle 50, weather, etc., it is determined ifthe rear sunlight condition is present. For example, when a current timeis around noon, and accordingly the sun is recognized to be located inthe south, and it is recognized that the vehicle 50 is running northbased on information transmitted from a navigation system, it isdetermined that the rear sunlight condition is present.

When it is determined in step S21 that the rear sunlight condition ispresent, the process proceeds to step S22. Then, a current luminance ofa pixel in a camera image corresponding to the hood 11 is calculated asthe reference value of the luminance parameter. Then, the processproceeds to step S14. By contrast, when it is determined in step S21that the rear sunlight condition is absent, the process skips step S22and proceeds to step S14.

Then, in step S14, a degree of whitish blur is calculated based on theluminance value calculated in step S13 (i.e., the luminance valueperiodically calculated during running of the vehicle) and the referencevalue calculated in step S22.

Here, when a hood surface becomes whitish due to aging or the like, thewhitish blur degree as calculated becomes excessive, and contrastcorrection is highly likely to be excessively performed. Hence, when thereference value as calculated in step S13 exceeds an upper limitdetermined in advance, the whitish blur degree as calculated is thencorrected by subtracting a given degree therefrom in proportion to anexcessive degree in step S14.

More specifically, if the reference value is different from a givensuitable value (i.e., upper limit), the whitish blur degree calculatedbased on the luminance value calculated in step S13 is corrected inaccordance with a difference between the reference value and the givensuitable value. For example, when a hood surface is whitish due toelapse of time or the like, a degree of whitish blur becomes too large,and a contrast may be excessively corrected. Hence, the degree ofwhitish blur is reduced thereby being corrected. Then, in step S15, acontrast of the camera image is corrected in accordance with the degreeof whitish blur as corrected.

FIG. 10 illustrates a running state of the vehicle 50, in which avertical direction indicates a north-south direction, and thus an upperside in the drawing corresponds to north and the lower side south,respectively. Here, as shown, the vehicle 50 travels south in a sectionA, east in a section B, and north in a section C. In such a situation, arear sunlight condition is determined to be present when it isdetermined that weather is fine and the vehicle 50 runs along thesection C out of these sections A to C at around noon, for example.Then, a value of luminance of the pixel corresponding to the hood iscalculated when the vehicle 50 runs along the section C, and is thendesignated as the reference value of the luminance parameter. Here, eachtime the rear sunlight condition is present, the reference value of theluminance parameter is calculated and the reference value is updated.

Hence, according to the second modification, the contrast of the cameraimage can be appropriately corrected. Because, even if the hood surfacebecomes whitish due to elapse of time or the like, excessive correctionof the contrast of the camera image can be suppressed or reduced.

Next, a third modification will be described herein below in detail withreference to FIG. 11 and applicable drawings. The above-described timemean value of the luminance parameter may be initialized when acondition of the natural light emitted to the hood 11 is watched and isdetermined to have changed. A specific sequence of the above-describedprocess of initializing, watching, and determining is shown in FIG. 11using a flowchart. This process is performed as a subroutine called instep S11 of FIG. 7 .

Specifically, in step S31, a current hood pixel value (i.e., a value ofa pixel in a camera image corresponding to the hood 11) is acquired.Subsequently, in step S32, it is determined if the natural light emittedto the hood 11 changes. For example, it may be desirably determined thata change in natural light occurs, for example, based on information fromthe navigation system of presence of either a tunnel entrance or atunnel exit during running of the vehicle. Otherwise, it may bedesirably determined that a change in natural light occurs based oninformation from the navigation system of presence of a change inrunning direction of the vehicle.

When it is determined that the natural light has not changed, theprocess proceeds to step S33, and a hood pixel value is calculated as atime mean value by averaging pixel values calculated during a givenperiod per time. By contrast, when it is determined that the naturallight has changed, the process proceeds to step S34 and initializes thetime mean value of the hood pixel value.

Accordingly, by calculating the whitish blur degree based on the timemean value of the hood pixel values, unstable calculation of the whitishblur degree can be suppressed or reduced even if the hood pixel valuetemporarily changes due to noise or the like. Further, since the timemean value of the hood pixel values is initialized when either thevehicle 50 enters and exits the tunnel or the running direction of thevehicle 50 regarding sunlight changes, the time mean value of the hoodpixel values can be appropriately calculated, thereby efficientlyenabling suppression or reduction of erroneous contrast correction.

Next, a fourth modification will be described herein below in detailwith reference to FIG. 12 and applicable drawings. The camera imagecaptured by the image capture unit 20 can be visually recognized by auser in addition to the usage of the driver assistance control.Specifically, the camera image of visual recognition to be used by theuser can be stored in a memory, for example, as a driving record of thevehicle 50. In such a configuration, it is desirable that the controlunit 30 differently calculates a correction value in accordance with awhitish blur degree and utilizes a different correction value obtainedin this way when the control unit 30 corrects a contrast of the cameraimage for driving support control use from a correction value used whenthe control unit 30 corrects a contrast of the camera image of visualrecognition to be used by the user.

Such a processing sequence is specifically shown in FIG. 12 by using aflowchart. This processing sequence is carried out in place of theabove-described processing sequence of FIG. 7 . In FIG. 12 , the sameprocess to that performed in FIG. 7 is numbered by the same step number,and the description thereof is not repeated (i.e., omitted). However, asshown in FIG. 12 , the step S15 of FIG. 7 is not employed, while stepsS41 to S44 are newly employed in addition to the steps except for thestep S15 of FIG. 7 .

As shown In FIG. 12 , in steps S11 to S14, a hood pixel value isobtained and is converted into a value of luminance, and a whitish blurdegree is then correspondingly calculated, respectively. Then, theprocess proceeds to step S41. In step S41, in accordance with thewhitish blur degree, a first correction amount used in correcting acontrast of a camera image for driving assistance control use and asecond correction amount used in correcting a contrast of a camera imagefor visual recognition to be used by a user are calculated. Here, thefirst correction amount and the second correction amount are calculatedto be different from each other. For example, since the camera image fordriver assistance control is used in white line recognition, objectrecognition, and the like, it is desirable that a contrast issignificantly corrected so that edges of these white lines and objectsare emphasized. By contrast, it is desirable that the camera image foruser recognition use is not different from an image visually recognizedby the user by sight. In view of this, the first correction amount ismade to be relatively large, while the second correction amount is madeto be relatively small.

Subsequently, in step S42, a camera image for driver assistance controlis generated by subtracting the first correction amount from a pixelvalue in each of the whole pixels in the camera image. Further, in stepS44, a camera image for user recognition use is generated by subtractingthe second correction amount from the pixel value in each of the wholepixels in the camera image.

Hence, according to the above-described fourth modification, thecontrast of the camera image can be appropriately corrected inaccordance with usage of the camera image. Further, with the cameraimage corrected for driver assistance control, the white linerecognition and the object recognition or the like can be appropriatelyperformed, thereby ultimately enabling appropriate driver assistancecontrol. Further, with the camera image corrected for visual recognitionto be used by the user, a camera image not causing the user visualdiscomfort can be provided to the user.

Further, it is yet desirable if the user can designate a contrast of thecamera image for visual recognition to be used by the user. In such asituation, a magnitude relation between the first correction value andthe second correction value may be arbitrarily determined. In addition,the second correction amount can be made greater than the firstcorrection amount.

Further, in the above-described embodiment and various modifications,the luminance is calculated by converting the hood pixel value and isused as the luminance parameter. However, the present disclosure is notlimited thereto and the hood pixel value itself can be used as theluminance parameter.

Further, in the above-described embodiment and various modifications,the image capture unit 20 and the control unit 30 are integrated witheach other in the camera 10. However, the present disclosure is notlimited thereto and the control unit can be separated from the imagecapture unit 20 to act as an image processing apparatus.

Further, in the vehicle 50, the image capture unit 20 can be configuredto capture images of the surroundings other than that in front of thevehicle. For example, the camera 10 can be a rear camera of the vehicle50 to capture images of surroundings on the rear side of the vehicle.

Further, the control unit 30 and its control method described heretoforein the present disclosure can be realized by a dedicated computercomposed of a processor programmed to perform one or more functionsspecified by computer program, and a memory. Also, the control unit 30and its control method described heretofore in the present disclosurecan be realized by a dedicated computer composed of a processorprogrammed to perform one or more functions and a memory. Alternatively,the control unit 30 and its control method described heretofore in thepresent disclosure can be realized by a dedicated computer with aprocessor composed of one or more dedicated hardware logic circuits. Asanother alternative, the control unit and its method describedheretofore in the present disclosure can be realized by one or morededicated computers, each of which is composed of a combination of aprocessor programmed to perform one or more functions, a memory, and aprocessor composed of one or more hardware logic circuits. Further, thecomputer program can also be stored in a computer-readablenon-transitory tangible recording medium as an instruction executed bythe computer.

Numerous additional modifications and variations of the presentdisclosure are possible in light of the above teachings. It is hence tobe understood that within the scope of the appended claims, the presentdisclosure may be performed otherwise than as specifically describedherein. For example, the present disclosure is not limited to theabove-described image processing system and may be altered asappropriate. Further, the present disclosure is not limited to theabove-described camera system and may be altered as appropriate.Further, the present disclosure is not limited to the above-describedvehicle and may be altered as appropriate.

What is claimed is:
 1. An image processing system used with anin-vehicle camera system, the camera system including: an image captureunit to capture images of surroundings of a vehicle as camera imagesthrough a windshield of the vehicle; and a hood to prevent an interiorof the vehicle from being reflected in the windshield and being capturedby the image capture unit together with the surroundings of the vehicle,the hood being disposed below the image capture unit and being presentin an angle of vision of the image capture unit; the image processingsystem comprising: a luminance parameter acquirer to acquire a luminanceparameter indicating a degree of luminance of an image of the hoodreflected in the camera image; a whitish blur degree calculator tocalculate a degree of whitish blur generated in the camera image as awhitish blur degree in accordance with the luminance parameter, thewhitish blur being generated when natural light is reflected by both thehood and an inner surface of the windshield; and a contrast corrector tocorrect a contrast of the camera image in accordance with the whitishblur degree.
 2. The image processing system as claimed in claim 1,wherein the luminance parameter acquirer converts a pixel value of thehood image included in the camera image to a value of luminance toacquire the luminance parameter, and the whitish blur degree calculatorcalculates the whitish blur degree in accordance with the value ofluminance parameter, wherein the luminance acquirer converts the pixelvalue into the value of luminance in accordance with an image capturingcondition based on which the image capture unit is controlled.
 3. Theimage processing system as claimed in claim 2, further comprising animage capturing condition designator to designate image capturingconditions in accordance with a type of driver assistance function thatassists a driver to operate the vehicle, wherein the luminance parameteracquirer converts the pixel value of the hood image into the value ofluminance in accordance with the image capturing condition of the imagecapture unit designated by the image capturing condition designator. 4.The image processing system as claimed in claim 1, wherein the contrastcorrector calculates correction values having a magnitude gradient in avertical direction of the camera image in accordance with the whitishblur degree, the contrast corrector correcting the contrast of thecamera image in accordance with the correction values.
 5. The imageprocessing system as claimed in claim 1, further comprising: a rearsunlight presence determiner to determine that a rear sunlight ispresent when a direction in which the image capture unit captures imagesis a direction in which sunlight directly enters the vehicle as the rearsunlight from a rear side of the vehicle; and a reference valuecalculator to calculate a reference value of the luminance parameter ofthe hood image, only when the image capture unit captures images in thesame direction as the rear sunlight; wherein the whitish blur degreecalculator calculates the whitish blur degree in accordance with adifference between the luminance parameter acquired by the luminanceparameter acquirer and the reference value calculated by the referencevalue calculator when the rear sunlight is present.
 6. The imageprocessing system as claimed in claim 1, further comprising a naturallight condition determiner to determine a condition of natural lightwith which the hood is irradiated, wherein the luminance parameteracquirer calculates the luminance parameter by obtaining a time meanvalue of the pixel values in a given time period, and initializes thetime mean value of the luminance parameter based on a determination ofthe natural light condition determiner that the natural light with whichthe hood is irradiated has changed.
 7. The image processing system asclaimed in claim 1, wherein the camera images captured by the imagecapture unit are used in driving support control and visual recognitionfor a user, wherein the contrast corrector calculates a differentcorrection value to correct the contrast of the camera image for drivingassistance control in accordance with the whitish blur degree from acorrection value used in correcting the contrast of the camera image forvisual recognition performed by the user.
 8. An in-vehicle camera systemcomprising: an image capture unit to capture images of surroundings of avehicle as camera images through a windshield of the vehicle; a hood toprevent an interior of the vehicle from being reflected in thewindshield and being captured by the image capture unit together withthe surroundings of the vehicle, the hood being disposed below the imagecapture unit and being present in an angle of vision of the imagecapture unit; and an image processing system including; a luminanceparameter acquirer to acquire a luminance parameter indicating a degreeof luminance of an image of the hood reflected in the camera image; awhitish blur degree calculator to calculate a degree of whitish blurgenerated in the camera image as a whitish blur degree in accordancewith the luminance parameter, the whitish blur being generated whennatural light is reflected by both the hood and an inner surface of thewindshield the windshield; and a contrast corrector to correct acontrast of the camera image in accordance with the whitish blur degree.9. A vehicle having an automatic driving function and a drive recorder,the vehicle comprising: an in-vehicle camera system disposed in a cabinclose to a windshield, the camera system including: an image captureunit to capture images of surroundings of a vehicle as camera imagesthrough a windshield of the vehicle; a hood to prevent an interior ofthe vehicle from being reflected in the windshield and being captured bythe image capture unit together with the surroundings of the vehicle,the hood being disposed below the image capture unit and being presentin an angle of vision of the image capture unit; and an image processingsystem including; a luminance parameter acquirer to acquire a luminanceparameter indicating a degree of luminance of an image of the hoodreflected in the camera image; a whitish blur degree calculator tocalculate a degree of whitish blur generated in the camera image as awhitish blur degree in accordance with the luminance parameter, thewhitish blur being generated when natural light is reflected by both thehood and an inner surface of the windshield; and a contrast corrector tocorrect a contrast of the camera image in accordance with the whitishblur degree.